Back on the surface, the weight of the ocean was replaced by the weight of knowledge. Amara and Kael sat under the stars, the data recorder between them, its song now a low hum in the quiet of the night.

"The city didn't drown because of the rising seas," Amara said, her voice a mix of awe and despair. "It was greed, the relentless pursuit of more power."

Kael nodded, his eyes reflecting the flickering light of their campfire. "They had the technology to harness the sun's energy, but they pushed it too far. They didn't see the limits until it was too late."

The recorder's revelations painted a grim picture of the past. The sunken city had been a beacon of progress, its people pioneers in solar technology. But their ambition had turned to avarice, and their insatiable hunger for energy had led to an ecological catastrophe.

"It's a cautionary tale," Kael continued. "A reminder that our reach can exceed our grasp, that we must be stewards, not exploiters, of the resources we have."

Amara felt the truth of his words. The city's legacy was not just one of innovation, but also of warning. The price of their progress had been the world itself.

As they delved deeper into the recorder's contents, they uncovered more about the unstable core that still lay within the city. It was a ticking time bomb, a remnant of the city's hubris that could still unleash destruction.

"We have to do something," Amara said, determination steeling her resolve. "If we ignore this, we're no better than they were. We risk repeating history."

But the path forward was fraught with peril. Sharing the knowledge of the core could lead to a scramble for its power, reigniting the same greed that had doomed the city. Yet, keeping it secret meant living with the fear of a disaster that could strike at any moment.

As dawn approached, Amara and Kael made their choice. They would find a way to neutralize the core, to ensure that the past's mistakes would not claim the future. It was a daunting task, but the song of the sunken city, now a dirge for a fallen world, reminded them of what was at stake.